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Unformatted text preview: johnson (mjj622) HW 15 Coker (56625) 1 This printout should have 17 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. This assignment covers the first chapter on wave motion, Ch. 16, which emphasizes trans verse waves, the wave equation, wave power, reflection, superposition, standing waves and group speed. 001 10.0 points A transverse wave on a very long string is described by y ( x, t ) = (2 cm) sin bracketleftbig( 1 . 6 m 1 ) x ( 50 s 1 ) t bracketrightbig What is the acceleration of the point at x = 0 at t = 3 4 seconds? 1. 50 m/s 2 2. 10 cm/s 2 3. 200 cm/s 2 4. 50 m/s 2 correct 5. 2 cm/s 2 6. Zero; this is a standing wave. 7. 200 cm/s 2 8. 62 . 5 cm/s 2 9. 10 cm/s 2 10. 1.6 m/s 2 Explanation: For y ( x, t ) = A sin( k x t ), the accelera tion of any point on the string is a y ( x, t ) = 2 y t 2 = A 2 sin ( k x t ) . sin( ) = sin , so at x = 0 a y (0 , t ) = A 2 sin ( t ) = A 2 sin ( t ) , and for t = 3 4 , a y = (2 cm) ( 50 s 1 ) 2 sin bracketleftbigg ( 50 s 1 ) parenleftbigg 3 4 s parenrightbiggbracketrightbigg = ( 5000 cm / s 2 ) sin parenleftbigg 75 2 parenrightbigg = ( 5000 cm / s 2 ) sin parenleftbigg 36 + 3 2 parenrightbigg = ( 5000 cm / s 2 ) sin parenleftbigg 3 2 parenrightbigg = ( 5000 cm / s 2 ) ( 1) 1 m 100 cm = 50 m / s 2 . 002 10.0 points A harmonic wave y = A sin[ k x t ] , where A = 1 m, k has units of m 1 , has units of s 1 , and has units of radians, is plotted in the diagram below. +1 1 A (meters) x (meters) 2 4 6 At the time t = 0 Which wave function corresponds best to the diagram? 1. y = A sin bracketleftbigg parenleftbigg 2 15 m parenrightbigg x t parenleftbigg 1 3 parenrightbiggbracketrightbigg 2. y = A sin bracketleftbigg parenleftbigg 2 15 m parenrightbigg x t parenleftbigg 5 3 parenrightbiggbracketrightbigg 3. y = A sin bracketleftbigg parenleftbigg 2 9 m parenrightbigg x t parenleftbigg 5 3 parenrightbiggbracketrightbigg 4. y = A sin bracketleftbigg parenleftbigg 2 9 m parenrightbigg x t parenleftbigg 4 3 parenrightbiggbracketrightbigg johnson (mjj622) HW 15 Coker (56625) 2 5. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x t parenleftbigg 2 3 parenrightbiggbracketrightbigg 6. y = A sin bracketleftbiggparenleftbigg 2 15 m parenrightbigg x t parenleftbigg 2 3 parenrightbiggbracketrightbigg 7. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x t parenleftbigg 1 3 parenrightbiggbracketrightbigg 8. y = A sin bracketleftbiggparenleftbigg 2 9 m parenrightbigg x t parenleftbigg 1 3 parenrightbiggbracketrightbigg 9. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x t parenleftbigg 5 3 parenrightbiggbracketrightbigg 10. y = A sin bracketleftbiggparenleftbigg 2 3 m parenrightbigg x t parenleftbigg 4...
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This note was uploaded on 02/10/2011 for the course PHY 303K taught by Professor Turner during the Fall '08 term at University of Texas at Austin.
 Fall '08
 Turner

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